Size control in the formation of magnetite nanoparticles in the presence of citrate ions

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• 作者：Victor L. Kirillov^a ; ^{VKirillov@catalysis.ru" class="auth_mail} ; Dmitry A. Balaev^b ; Sergey V. Semenov^b ; Kirill A. Shaikhutdinov^b ; Oleg N. Martyanov^a
• 关键词：Magnetic materials ; Magnetic properties ; Precipitation ; Electron paramagnetic resonance
• 刊名：Materials Chemistry and Physics
• 出版年：15 May, 2014
• 年：2014
• 卷：145
• 期：1-2
• 页码：75-81
• 全文大小：2096 K

文摘

A one-pot synthesis method for the controllable growth of magnetite nanoparticles directly during the process of co-precipitation using citrate ions was developed. The effects of the concentration of citrate ions and the solution pH on the characteristics of magnetite particles with sizes in the range of 4-10聽nm synthesized by the method of co-precipitation were studied. The results showed that the specified concentration of citrate ions allowed the preparation of magnetite particles with a definite size that exhibited superparamagnetic behaviour in a particular temperature range. As the concentration ratio of citrate to iron ions was increased from 0 to 0.11, the average size of the prepared magnetite particles decreased from 10.5 to 4.4聽nm. As a result, the superparamagnetic blocking temperature decreased from 300 to 20聽K, the saturation magnetisation decreased from 50 to 20聽emu聽g^鈭?, and the average magnetic moment decreased from 8000聽渭_B to 340聽渭_B (at T聽=聽300聽K).

The obtained experimental data proved that the size effects of the magnetite nanoparticles can be attributed to the capping of the magnetite surface by adsorbed citrate ions. Thus, the suggested approach allows magnetite nanoparticles to be prepared with an optimum particle size around superparamagnetic threshold that prevents their irreversible agglomeration and simultaneously allows them to be removed from a solution at an acceptable rate.